Multiple reduction photolithography technique

Abstract

A photolithography method for creating very small line dimensions includes making a mask by exposing a mask blank through a reticle in a reduction photolithography exposure tool, at a reduction of N. The fabricated mask is then placed in a second photolithography exposure tool at a second reduction M, to expose a wafer substrate at a reduction of M. The resulting patterned substrate will have a critical dimension equaling the critical dimension of the original reticle, divided by the factor N times M. In this manner, very small size patterns can be created even though a larger pattern starting reticle is used.

We claim: 
     
       1. A method of forming a patterned field on a mask at a pre-defined critical dimension for use in photolithography, comprising: providing a first reticle having a pattern comprising a first segment of said field, wherein said first reticle pattern contains a first predesigned pattern edge, said first reticle pattern having a first critical dimension;   exposing a mask blank at a first reduction using said first reticle to transfer said first segment onto said mask blank at a second critical dimension;   providing a second reticle having a pattern comprising a second segment of said field, wherein said second reticle pattern contains a second predesigned pattern edge, said second reticle pattern having said first critical dimension; and   exposing the mask blank at a first reduction using said second reticle to transfer said second segment onto said mask blank at said second critical dimension, wherein said first and second reticle patterns are aligned at said first pattern edge and said second pattern edge to stitch the first pattern edge and the second pattern edge together.   
     
     
       2. A method of forming a patterned field on a mask as in claim 1, wherein said predesigned pattern edges include slanted line edges. 
     
     
       3. A method of forming a patterned field on a mask as in claim 2, wherein said slanted line edges comprise stair step line edges. 
     
     
       4. A method of forming a patterned field on a mask as in claim 1, wherein said steps of exposing the mask blank include performing a plurality of partial exposure steps to create a full exposure. 
     
     
       5. A method of forming a patterned field on a mask as in claim 1, wherein said mask blank includes a resonant reflective layer therein. 
     
     
       6. A method of forming a patterned field on a mask as in claim 5, further including the step of opening trenches within said resonant reflective layer.